(1) Field of the Invention
The present invention relates to a delivery method and distribution system of a contents information as well as a central station thereof suitable for use in providing a service for carrying out a contents delivery with an optical access system.
It is anticipated that a large-capacity contents delivery service such as Super High Definition (SHD) pictures becomes popular by means of a FTTH (Fiber to The Home) or the like in near future. For this reason, there will be a need for communication common carriers or the like to receive contents as an optical signal from contents suppliers, and deliver the optical signal as it is to each user from a delivery central station or the like.
(2) Description of the Related Art
As for the conventional contents collection and delivery service, the one using an electrical signal as the information-transmission medium is mainstream. There is also the one using an optical signal as the information-transmission medium in a part of a CATV system, for example, on optical transmission lines such as a HFC (Hybrid Fiber Coax). However also in this case a delivery section to each user is processed with electrical signals. Moreover, as a part of this optical transmission line, the delivery by an optical fiber and a PON (Passive Optical Network) is used.
In addition, a BPON (broadband PON), an STM-PON (Synchronous Transfer Mode PON), an ATM-PON (Asynchronous Transfer Mode PON), an EPON (Ethernet PON), or the like can be used as the above-described PON. Moreover, as a network for the contents delivery, there is also a delivery system including a router, a LAN switch, a media converter, or the like. In the above-described BPON, a Dynamic Bandwidth Assignment (DBA) technique is under investigation, however, this technique is used within the scope of the transmission capacity intrinsic to the transmission line.
However, in any one of such conventional techniques for the contents delivery, a light wavelength, a transmission rate, and a coding format of signals are limited in each system (fixed to some extent), and thus the upper limit of the user service is generally 100 Mb/s or so.
Namely, in networks for a backbone system (a trunk network system), a wavelength routing by means of a DC-SW (Delivery and Coupling Switch), a MEMS (Micro Electro Mechanical Systems) switch, or the like is under Investigation as a large-scale photonic MPLS (Multi Protocol Label Switching) router, however, assuming development of the contents delivery service in future, it is essential to develop a network system for the contents delivery (corresponding to a super-large capacity), which limits neither the transmission rate nor the coding format, also in an access system.
Moreover, a relation between a download time of the contents to be delivered and the transmission rate in future optical access systems is generally assumed as shown in FIG. 18. As shown in FIG. 18, in a stream delivery having a method of delivering from a server on real time, if the download time is set to 3 minutes, it is assumed that the transmission rate of 80-130 Kb/s or so for MP3 music, 3-10 Mb/s or so for a standard image-quality picture, and 20 Mb/s or so for a high definition picture are required respectively.
Moreover, as shown in FIG. 18, in a block delivery having a method of using contents after delivering contents at one time and storing into a terminal, if the download time is set to 3 minutes, it is assumed that the transmission rate of 80-130 Kb/s or so for MP3 music, 220 Mb/s or so for a standard image-quality picture, and 800 Mb/s or so for a high definition picture are required respectively.
In this way, it is thought that if the same download time is required for the stream delivery and the block delivery, there will be produced a difference in the required bandwidths in these methods, which causes the network configurations thereof to differ. However, whichever is chosen from the delivery methods of which the required bandwidths are greatly different, getting through with a common (or unique) network configuration will be a subject in order to make the network configuration efficient.
In addition, as a technique related to the present invention there are the techniques described in Japanese Patent (Kokai) Hei 5-63659 (patent document 1) and Japanese Patent Publication No. 3169665 (patent document 2). Such techniques assume a multiple star network in which transmission to each subscriber is carried out using signals having a common wavelength band, so it is impossible to realize, from the techniques described in the above-described documents, the very network having such a simple configuration that each subscriber can receive a delivery of a large-capacity contents information on demand.
The present invention has been made in view of such a problem, and is intended to provide a delivery method and delivery system of a contents information as well as a central station thereof, which do not restrict the transmission rate, the coding format, or the like in the access system, i.e., which is enabled to cope with a super-large capacity by means of a simple configuration, and also which is enabled to cope with delivery methods of which the required bandwidths are greatly different.    [patent document 1] Japanese Patent Laid-open (Kokai) Hei 5-63659    [patent document 2] Japanese Patent No. 3169665